Remove half-list/half-set in get_all_addresses and add type signature (#1441)
Remove half-list/half-set in get_all_addresses and add type signature (#1441)

This makes mypy happier.

It is unnecessarily complicated to use a list in one part and
a set in another part. Either section might produce duplicates
which need removing - for example, multiple interfaces might
have the same address.
Parsl/parsl,Parsl/parsl,Parsl/parsl,Parsl/parsl